#!/usr/bin/python
# coding: utf-8

# Copyright © Sébastien Luttringer
#
# This program is free software; you can redistribute it and/or
# modify it under the terms of the GNU General Public License
# as published by the Free Software Foundation; either version 2
# of the License, or (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.

'''Find dependencies of a package or directory'''

from argparse import ArgumentParser
from elftools.elf.dynamic import DynamicSection, DynamicSegment
from elftools.elf.elffile import ELFFile
from os import walk, environ, getcwd, chdir, access, R_OK
from os.path import join, exists, isdir, isfile, normpath, realpath
from pprint import pprint
from pycman import config
from shlex import split
from sys import stderr
from tarfile import open as tar
from tempfile import TemporaryDirectory

PACKAGES = None

def missing_pkginfo(path, deps):
    '''show deps against path'''
    fpath = join(path, ".PKGINFO")
    if not access(fpath, R_OK):
        return
    pkginfo = parse_pkginfo(fpath)
    if "depend" not in pkginfo:
        return
    diff = set(deps.keys() - set(pkginfo["depend"]))
    if len(diff) > 0:
        print("\n:: Missing in .PKGINFO")
        pprint(diff)

def parse_pkginfo(path):
    '''parse a .PKGINFO file'''
    pkginfo = dict()
    with open(path) as fd:
        for line in fd.readlines():
            # skip empty and comment
            if len(line) == 0 or line[0] == "#":
                continue
            lhs, rhs = line.split("=", 1)
            pkginfo.setdefault(lhs.strip(), []).append(rhs.strip())
    return(pkginfo)

def find_sharedlibs(fd):
    ef = ELFFile(fd)
    for section in ef.iter_sections():
        if isinstance(section, DynamicSection):
            for tag in section.iter_tags():
                if tag.entry.d_tag == 'DT_NEEDED':
                    yield(tag.needed)

def find_pkg(path):
    '''find the package owning path'''
    if not exists(path):
        return None
    path = normpath(realpath(path)).lstrip('/')
    global PACKAGES
    if PACKAGES is None:
        PACKAGES = config.init_with_config(environ.get("PACMAN_CONF",
            "/etc/pacman.conf")).get_localdb().pkgcache
    for pkg in PACKAGES:
        if path in [ x[0] for x in pkg.files]:
            return(pkg.name)
    return None

def find_deps(path):
    '''find deps packages'''
    deps = {}
    cwd = getcwd()
    chdir(path)
    for (dirpath, dirnames, filenames) in walk("."):
        for filename in filenames:
            fpath = join(dirpath, filename)
            with open(fpath, "rb") as fd:
                magic = fd.read(4)
                fd.seek(0)
                # ELF
                if magic == b"\x7fELF":
                    for libname in find_sharedlibs(fd):
                        pkgname = find_pkg("/usr/lib/%s" % libname)
                        deps.setdefault(pkgname, dict())
                        deps[pkgname].setdefault(libname, set())
                        deps[pkgname][libname] |= {fpath}
                elif magic[:2] == b"#!":
                    exec_path = fd.readline()[2:].split()[0].decode()
                    pkgname = find_pkg(exec_path)
                    deps.setdefault(pkgname, dict())
                    deps[pkgname].setdefault(exec_path, set())
                    deps[pkgname][exec_path] |= {fpath}
    chdir(cwd)
    return(deps)

def parse_argv():
    '''Parse command line arguments'''
    parser = ArgumentParser()
    parser.add_argument("path", metavar="package|directory")
    return parser.parse_args()

def main():
    '''Program entry point'''
    args = parse_argv()
    if isfile(args.path):
        pkgdir = TemporaryDirectory()
        tarball = tar(args.path)
        tarball.extractall(pkgdir.name)
        args.path = pkgdir.name
    if isdir(args.path):
        deps = find_deps(args.path)
        # display deps
        print(":: Found deps")
        pprint(deps)
        # show missing deps in .PKGINFO
        missing_pkginfo(args.path, deps)
    else:
        stderr.write("Unsupported file type\n")
        return 2
    return 0

if __name__ == '__main__':
    main()

# vim:set ts=4 sw=4 et ai: